where \(S\)  is the set of URLs shared by \(u\)  and \(A(s)\)  is data from [1]} which estimates the political alignment of \(s\) 's web domain, \(D(s)\) . A score of -1 for \(A(D(s))\)  implies URLs that belong to the same web domain as \(s\)  tend to be shared exclusively by left-leaning social media users; 1 implies these URLs are shared exclusively by right-leaning users; and within this range implies mixed sharing across ideological groups (with 0 indicating balanced sharing).
